Molecular Breast Imaging: A Scientific Review

Molecular breast imaging (MBI) is a nuclear medicine technique that has evolved considerably over the past two decades. Technical advances have allowed reductions in administered doses to the point that they are now acceptable for screening. The most common radiotracer used in MBI, 99mTc-sestamibi, has a long history of safe use. Biopsy capability has become available in recent years, with early clinical experience demonstrating technically successful biopsies of MBI-detected lesions. MBI has been shown to be an effective supplemental screening tool in women with dense breasts and is also utilized for breast cancer staging, assessment of response to neoadjuvant chemotherapy, problem solving, and as an alternative to breast MRI in women who have a contraindication to MRI. The degree of background parenchymal uptake on MBI shows promise as a tool for breast cancer risk stratification. Radiologist interpretation is guided by a validated MBI lexicon that mirrors the BI-RADS lexicon. With short interpretation times, a fast learning curve for radiologists, and a substantially lower cost than breast MRI, MBI provides many benefits in the practices in which it is utilized. This review will discuss the current state of MBI technology, clinical applications of MBI, MBI interpretation, radiation dose associated with MBI, and the future of MBI.

41 Diagnosing Bone Metastases in Breast Cancer – CT Vs Nuclear Medicine Bone Scan

Introduction Guidelines advise use of CT or MRI to detect bone metastasis in breast cancer. Bone-scintigraphy (BS) is not routinely indicated. However, our patients with new node positive breast cancer, or symptoms suggestive of bone metastases, undergo both CT and BS. We aimed to evaluate discrepancies between CT and BS results, and assess whether CT is more accurate in diagnosing bone metastases in breast cancer patients. Method Over a 2-year period, breast cancer patients who underwent CT and BS within 28 days of each other, were included. Scan reports were reviewed, and where unclear, MDT outcome was consulted. Results Of 149 patients, 15 (10.1%) had discordant scan results. Where CT was negative, and BS suspicious (n = 6) or positive (n = 3), patients were either found to have visceral metastases on CT, BS was found to be a false positive, or MDT concluded there were no bone metastases. Where CT was positive and BS negative (n = 4), MDT confirmed metastases. Conclusions CT is as good as BS in demonstrating bone metastases, and also detects visceral metastases. Using CT only would reduce radiation exposure, costs, and burden on service provision. We advise a change in local policy, with CT scan as the primary investigation for breast cancer staging.

Endosalpingiosis Is Negative for GATA3

Context.— Endosalpingiosis is a benign Müllerian inclusion that can mimic metastatic low-grade mammary carcinoma, particularly when encountered in axillary lymph nodes excised for breast cancer staging. Immunohistochemistry can be useful in histologically ambiguous cases, and a targeted immunopanel should include a marker of gynecologic tract origin and a marker of mammary origin. GATA3 is a sensitive immunomarker for breast carcinoma, but the immunoreactivity of GATA3 in endosalpingiosis has not been systematically evaluated. Objective.— To evaluate whether GATA3 immunohistochemistry could be used to differentiate endosalpingiosis from metastatic mammary carcinoma. Design.— Whole slide sections of 15 cases of endosalpingiosis involving nonneoplastic tissues were subjected to GATA3 immunohistochemistry. Nuclear GATA3 labeling was scored as percentage and intensity labeling, with any labeling considered positive; GATA3 labeling was recorded in all cells present in the sections. Results.— Half (47%, n = 7 of 15) of the endosalpingiosis cases involved lymph nodes (2 axillary, 5 pelvic) and half (53%, n = 8 of 15) involved pelvic organs or soft tissue (3 myometrial, 2 paratubal, 2 periadnexal soft tissue, and 1 pelvic sidewall). GATA3 immunohistochemistry was negative in all cases of endosalpingiosis, with intact, positive control labeling in lymphocytes. The benign fallopian tube epithelium present on the sections of paratubal endosalpingiosis displayed focal (<5%), weak labeling for GATA3, specifically within the ciliated and secretory cells. Conclusions.— These findings support the diagnostic utility of GATA3 immunohistochemistry and its use in a targeted immunopanel to resolve the differential diagnosis of metastatic low-grade mammary carcinoma (GATA3+) and nodal endosalpingiosis (GATA3−).